Yes it is supported.

You may see the error but when you edit the web part and input the correct information the error will go and the form will apppear.

Hi, I'm having the exact same issue.  Adding the online web part on SP365 modern page results in the "object error..."  What is the "correct information" you reference?  You mean the listforms settings?  where do you get that information?  there is nothing on Nintex Help or User Group that details this information.  The "Configuring List Form Settings" documentation goes up to SharePoint 2019 (on-prem).  Any help would be appreciated.